Export support types from extractors

Make each extractor  plugin export a list of file types it supports,
so we no longer need to hardcode such a list in the framework.

Test: manual
Change-Id: I1e41a5d477ea56960ad3e4bc35f5183c03c3fe3a
diff --git a/services/mediaextractor/MediaExtractorService.cpp b/services/mediaextractor/MediaExtractorService.cpp
index 8b26178..0665930 100644
--- a/services/mediaextractor/MediaExtractorService.cpp
+++ b/services/mediaextractor/MediaExtractorService.cpp
@@ -59,6 +59,10 @@
     return CreateIDataSourceFromDataSource(source);
 }
 
+std::unordered_set<std::string> MediaExtractorService::getSupportedTypes() {
+    return MediaExtractorFactory::getSupportedTypes();
+}
+
 status_t MediaExtractorService::dump(int fd, const Vector<String16>& args) {
     return MediaExtractorFactory::dump(fd, args) || dumpExtractors(fd, args);
 }
diff --git a/services/mediaextractor/MediaExtractorService.h b/services/mediaextractor/MediaExtractorService.h
index 6007004..c9cebcf 100644
--- a/services/mediaextractor/MediaExtractorService.h
+++ b/services/mediaextractor/MediaExtractorService.h
@@ -37,6 +37,8 @@
 
     virtual sp<IDataSource> makeIDataSource(int fd, int64_t offset, int64_t length);
 
+    virtual std::unordered_set<std::string> getSupportedTypes();
+
     virtual status_t    dump(int fd, const Vector<String16>& args);
 
     virtual status_t    onTransact(uint32_t code, const Parcel& data, Parcel* reply,